This invention relates to treatments for vocal cord paralysis and more particularly to a prosthetic device for a vocal cord that locates a paralyzed vocal cord in a phonation position and is postoperatively adjustable to change the position of the paralyzed vocal cord.
During normal vocal cord operation the vocal cords, i.e., the glottic mucous membranes, elastic membranes, muscles, and cartilages within the larynx, are movable between a relatively closed convergent phonation position proximate the middle of the larynx, and a relatively open divergent breathing position. Thus the vocal cords normally undergo dynamic movement between their relatively closed phonation position to their relatively open breathing position to enable a speaker to breathe efficiently and noiselessly during exercise, while talking or otherwise phonating with good volume when sedentary.
If one of the vocal cords is paralyzed, it will usually recede into a slightly divergent open position resulting in reduced phonation capability.
Paralysis of a single vocal cord is thus generally treated by moving the paralyzed vocal cord to a compromise position that improves phonation (but at the expense of breathing). Since it is difficult to breathe deeply and rapidly when one vocal cord is in the fully converged phonation position and it is very difficult to speak with one vocal cord in a fully diverged breathing position, the compromise position of the paralyzed vocal cord provides less than optimum voice quality and less than optimum breathing efficiency in order that both such functions can occur. However the compromise position of a paralyzed vocal cord is usually determined empirically during surgery.
In one known treatment for vocal cord paralysis, a gel foam collagen or Teflon.RTM. paste is injected into the paralyzed vocal cord to increase its size and thus change the vocal cord position to one which permits stronger phonation without obstructing breathing. However the injected material cannot be post-surgically adjusted or shifted to improve phonation or breathing.
In another known treatment as shown in U.S. Pat. No. 3,818,894, a water-expandable reed-like structure is implanted in a dry state into the paralyzed vocal cord. After implantation, the reed-like structure undergoes a sponge-like expansion that increases the size of the paralyzed vocal cord and changes its position to a desired phonation position that also permits breathing. However, the size of the implant again cannot be post-surgically adjusted and thus the vocal cord position obtained as a result of vocal cord expansion cannot be changed without further surgery.
If a vocal cord is only temporarily paralyzed, it is usually impractical to inject gels or install prosthetic devices into the vocal cord, especially if there is an intent at some later time to restore the vocal cord to its preoperative condition. In such instances, a paralyzed vocal cord can be temporarily repositioned by inserting a wedge-like prosthetic device between the thyroid cartilage, which surrounds the front and sides of the larynx, and the paralyzed vocal cord, much as a shim is used to adjust the position of a structure.
During installation of the wedge-like prosthetic device, a patient may be asked to phonate or speak while the surgeon adjusts the position or size of the wedge to obtain the best possible voice quality and breathing function under the circumstances. However, the surgically determined position of a paralyzed vocal cord cannot be modified without undergoing further surgery. Furthermore, due to intraoperative swelling which will later resolve, the position determined at surgery may not turn out to be the optimum position after the surgery has healed.
Any surgical or injection relocation of a paralyzed vocal cord from its receded position to a phonation position often results in tissue swelling that, in some instances, can be anticipated and allowances made. However, because the effects of swelling on the repositioning of a paralyzed vocal cord are somewhat unpredictable, it would be beneficial to make final adjustments of the repositioned paralyzed vocal cord after the swelling subsides. Scar tissue can also form in varying amounts in the vicinity of a repositioned paralyzed vocal cord to adversely affect the voice quality of a patient. Since postoperative access to the paralyzed vocal cord to make a final adjustment requires further surgery, such adjustments are not feasible.
It is thus desirable to provide a prosthetic device for a paralyzed vocal cord that can be adjusted after surgery is completed to optimize voice quality and breathing function.